The present invention relates to cryogenic coolers, and more particularly to the passive movement control of the displacer in coolers of the split cycle type.
Cryogenic coolers are employed in a number of fields, e.g. electro-optics, electronics, vacuum techniques etc. Constructions of such coolers comprise two basic constituents: a compression--and an expansion unit. Some of these coolers operate on a closed circuit scheme and the passage of the gas used occurs from compression stage to expansion without use of valves. A typical example is the Stirling cycle and those designed similar to it.
There is a well known group of coolers of split build, i.e. the compression--and the expansion stage being strictly distinct and being connected only by gas conducting conduits. In this type of coolers the operation of the expansion unit is by pneumatic, or electric or motor drive. The principle of the function of the expansion unit is based on change of volume of an expansion cell which occurs periodically and under phase difference in relation to pressure pulses acting on the said cell. The creation of a proper phase differential between the volume and pressure pulses is imperative.
In pneumatically driven split cycle coolers the change of volume of the expansion space is obtained by means of a pneumatic drive which is actuated by the same source of pressure pulses which acts on the expansion space, it is necessary to provide means ensuring the creation of the necessary phase differential. This differential is in the range of 80.degree.-120.degree., so as to ensure maximal efficiency.